For example, with a dramatic improvement in performance of central processing units (CPUs) in high-end servers, the speed of data transmission between racks, between boards, and in a board has been increasing recently. In such a circumstance, optical interconnect technology capable of providing faster data transmission has been discussed since conventional technology for increasing the speed with electrical wirings is approaching its limit.
To realize high-speed optical interconnect, a technique for driving a light-emitting element at high speed is used, for example. When the light-emitting element is driven at high speed, waveform distortion occurs because of relaxation oscillations and bandwidth limitation of the light emitting element and transmission quality decreases. As a countermeasure for this, pre-emphasis is known in which a rising part and a falling part of a driving signal of the light-emitting element is in advance corrected (emphasized or suppressed). For example, a driver is known that splits a driving signal, provides a delay difference to the split driving signals, and combines (adds or subtracts) the driving signals (see, for example, Japanese Unexamined Patent Application Publication No. 2004-88693).